Recently, microminiaturization and integration of chemical reaction systems have been attracting attention as new technical subjects in synthetic chemistry, analytical chemistry, semiconductor industry, and biotechnology industry. It is thought that such microminiaturization and integration will play an important role in improving precision and promoting efficiency in the control of chemical reaction in systems for immunoassay, environmental analysis, cell biochemistry experiment, chemical gas-phase growth, and synthetic chemistry experiment. In such technological trend, new research and development is about to be promoted, whose subject is chemical reaction whose reaction capacity is a minuscule space from nanoliter to microliter, a so-called microreactor; and whose objective is improvement of reaction yield, shortening of reaction time, and decrease of burden to the environment. For the liquid or gas to be supplied to such a minute space, minute and precise flow control that is nonexistent in the existing technology is considered to be indispensable.
Conventionally, as the valve type used for minute flow adjustment of fluid, the needle valve type is usually used. As for the needle valve, since the flow rate increases suddenly after opening of the valve, it is difficult to employ it as a means to adjust the flow rate (for example, the maximum flow of 10 mL/min-1 mL/min for liquid, or a minute flow rate of 1-0.01 sccm for gas) supplied to said minute space. Therefore, the development of a new minute flow rate control technology suitable for such purpose has become necessary.
As for prior arts for minute flow rate control valves whose mechanism is different from the needle valve type, Japanese Patent Laid-Open No. 2001-187977 (patent document 1) and Japanese Patent Laid-Open No. 2003-278934 (patent document 2) have been made public. Both of these prior arts are characterized by the configuration in which the throttle groove that controls the fluid flow rate is arranged in an arc-shape.    [Patent Document 1] Japanese Patent Laid-Open No. 2001-187977    [Patent Document 2] Japanese Patent Laid-Open No. 2003-278934